Filler sheet for solar cell module, and solar cell module using the same

ABSTRACT

A main object of the invention is to provide a filler sheet for a solar cell module which is excellent in various properties such as strength, endurance, weatherability, heat resistance, water resistance, light resistance, wind pressure resistance, hailstorm resistance, and vacuum laminating suitability, and has very good thermal melting/bonding property without being affected by production conditions and others, and which makes it possible to produce a solar cell module, suitable for various use purposes, stably at low costs; and a solar cell module using the same. In order to attain the object, the invention provides, as a filler sheet for solar cell element, a filler sheet made of a resin film produced by a resin composition comprising a copolymer of an α-olefin and an ethylenic unsaturated silane compound, or a modified or condensed body thereof, and one or more selected from the group consisting of a light resisting agent, an ultraviolet absorbent and a thermal stabilizer; and a filler sheet made of a resin film produced by a resin composition comprising a maleic anhydride modified polyolefin.

TECHNICAL FIELD

The present invention relates to a filler sheet for a solar cell module,and a solar cell module using the same, more specifically, a very usefulfiller sheet for a solar cell module which is excellent in strength andendurance and further excellent in various properties such asweatherability, heat resistance, light resistance, water resistance,wind pressure resistance, hailstorm resistance, and vacuum laminatingsuitability, and has very good thermal melting/bonding property withoutbeing affected by production conditions for heating, compression andothers for producing a solar cell module, and which makes it possible toproduce a solar cell module stably at low costs; and a solar cell moduleusing the same.

BACKGROUND ART

In recent years, attention has been paid to a solar cell as a cleanenergy source in light of an upsurge of consciousness of environmentalproblems, and at present solar cell modules in various forms have beendeveloped and suggested.

In general, the solar cell modules are each produced by first producing,for example, a crystal silicon solar cell element or amorphous siliconsolar cell element and then utilizing a lamination process of using sucha solar cell element to laminate a front face protecting sheet, a fillersheet, the solar cell element as a photo electromotive force element, afiller sheet, a rear face protecting sheet, and so on in order thatthese members have been described and next heating and compressing thesemembers while vacuum-sucking the members, or some other process.

At first, the solar cell modules were applied to electric calculators.Thereafter, the modules have been applied to various electronicapparatuses, and the application range thereof has rapidly beenspreading for the people's livelihood. It is said that the mostimportant theme in the future is a realization of large-scaleconcentrated type solar cell power generation.

Incidentally, about the filler sheets laminated on the front face sideand the rear face side of the solar cell element, as aphotoelectromotive force element, in the solar cell modules, sunlight isradiated into the filler sheet positioned on the front face side. Thus,the filler sheet needs to have transparency that the sheet transmitsthis light. However, the filler sheet positioned on the rear face sidemay not necessarily have transparency.

Needless to say, the filler sheets which constitute the solar cellmodules have adhesiveness to the front face protecting sheet or the rearface protecting sheet. Furthermore, it is said that the filler sheetsneed to have thermal plasticity for fulfilling a function of keeping thesmoothness of both of the front and rear faces of the solar cell elementas a photoelectromotive force element, be excellent in strength andendurance and further various properties such as weatherability, heatresistance, light resistance, water resistance, wind pressure resistanceand hailstorm resistance, and be further excellent in scratchresistance, impact absorptivity, and others.

At present, as the material constituting the filler sheets, there ismost generally used a filler sheet which has a thickness of 400 to 600μm and is made of ethylene-vinyl acetate copolymer from the viewpoint ofthe processability, the workability, the production costs thereof, andthe like (see, for example, Japanese Patent Application Laid-Open Nos.58-63178 (claims), and 59-22978 (claims)).

However, when the above-mentioned filler sheet, 400 to 600 μm inthickness, made of ethylene-vinyl acetate copolymer or the like is usedand this is directly laminated to produce a solar cell module by alamination process of laminating this filler sheet, a front faceprotecting sheet, a solar cell element, a rear face protecting sheet andothers, and heating and compressing the resultant laminate whilevacuum-sucking the laminate wholly, or some other process, the fillersheet, made of ethylene-vinyl acetate copolymer or the like, is affectedsuch as by conditions for the heating and compression, or the storage orpreservation of the produced solar cell module. As a result, forexample, the ethylene-vinyl acetate copolymer thermally shrinks orthermally decomposes to release acetic acid. As a result, adecomposition gas and a decomposition product of the acetic acid gas,and others are generated so as to produce a bad effect on the solar cellmodule, thereby resulting in, for example, corrosion or deterioration ofelectrodes constituting the solar cell module, a drop in electric powergeneration, or thereby causing the decomposition gas or the like toreact with amorphous portions of silicon constituting the solar cellelement so as to bring about a fall in electromotive force and otherproblems. Thus, there are problems that the solar cell module is notsufficiently satisfactory in thermal melting/bonding property when beingheated and compressed, storability, preservability and others, anddifficulty is found in producing the solar cell module stably at lowcosts.

Furthermore, when the ethylene-vinyl acetate thermally shrinks orthermally decomposes so that acetic acid is released to generate adecomposition gas such as acetic acid gas as described above, theworking environment therefor and so on are deteriorated so that effecton workers and others cannot be avoided. Accordingly, the environmentfor the production should be unavoidably improved. As a result, costsare remarkably increased and the productivity and the like thereof areremarkably hindered.

Additionally, the above-mentioned ethylene-vinyl acetate copolymer orsimilar resin itself is somewhat insufficient in strength, endurance andother properties, and is not very good in various properties such asweatherability, heat resistance, light resistance, wind pressureresistance, and hailstorm resistance. The resin is deteriorated by, forexample, ultraviolet rays out of sunlight rays so as to cause colorchanges such as yellowing, thereby resulting in a problem that thedesign or decoration property is remarkably damaged.

DISCLOSURE OF THE INVENTION

In light of the above-mentioned problems, the present invention has beenmade, and provides a very useful filler sheet for a solar cell modulethat is made of a material which is excellent in strength and enduranceand further excellent in various properties such as weatherability, heatresistance, water resistance, light resistance, wind pressureresistance, hailstorm resistance, and vacuum laminating suitabilitywithout being affected by solar cell module producing conditions, whichhas very good thermal melting/bonding property without being affected byproduction conditions for heating, compression and others for producinga solar cell module, and which makes it possible to produce a solar cellmodule suitable for various use purposes stably at low costs; and asolar cell module using the same.

The present inventors have made very researches about filler sheets forsolar cell module to solve problems as described above. As a result, theinventors have paid attention to a filler sheet made of a resin filmproduced by a resin composition comprising a copolymer of an α-olefinand an ethylenic unsaturated silane compound, or a modified or condensedbody thereof, and one or more selected from the group consisting of alight resisting agent, an ultraviolet absorbent and a thermalstabilizer; and as a filler sheet laminated on the front face and rearface sides of a solar cell element instead of any conventional fillersheet made of ethylene-vinyl acetate copolymer or the like, theinventors have made a filler sheet of a resin film made of theabove-mentioned resin composition, which comprises a copolymer of anα-olefin and an ethylenic unsaturated silane compound, or a modified orcondensed body thereof, and one or more selected from the groupconsisting of a light resisting agent, an ultraviolet absorbent and athermal stabilizer. The inventors have produced a solar cell module byuse of a lamination process of laminating, firstly, a front faceprotecting sheet, a filler sheet made of a resin film produced by aresin composition comprising a copolymer of an α-olefin and an ethylenicunsaturated silane compound, or a modified or condensed body thereof,and one or more selected from the group consisting of a light resistingagent, an ultraviolet absorbent and a thermal stabilizer, a solar cellelement, a filler sheet made of a resin film produced by a resincomposition comprising a copolymer of an α-olefin and an ethylenicunsaturated silane compound, or a modified or condensed body thereof,and one or more selected from the group consisting of a light resistingagent, an ultraviolet absorbent and a thermal stabilizer, and a rearface protecting sheet in sequence, and secondly heating and compressingthese members while vacuum-sucking the members wholly, or some otherprocess. As a result, the inventors have found out that theabove-mentioned filler sheet, which is made of a resin film produced bya resin composition comprising a copolymer of an α-olefin and anethylenic unsaturated silane compound, or a modified or condensed bodythereof, and one or more selected from the group consisting of a lightresisting agent, an ultraviolet absorbent and a thermal stabilizer, isexcellent in strength and endurance and further excellent in variousproperties such as weatherability, heat resistance, water resistance,light resistance, wind pressure resistance, hailstorm resistance, andvacuum laminating suitability; has very good thermal melting/bondingproperty without being affected by production conditions for heating,compression and others for producing the solar cell module; and makes itpossible to produce stably a very useful solar cell module suitable forvarious use purposes at low costs. Thus, the present invention has beencompleted.

The inventors have found out that the use of a filler sheet made of aresin film produced by a resin composition comprising a maleic anhydridemodified polyolefin as a filler sheet laminated on the front face sideand the rear face side of a solar cell element makes it possible toproduce the same advantageous effects as in the case of using a resinfilm produced by a resin composition comprising a copolymer of anα-olefin and an ethylenic unsaturated silane compound, or a modified orcondensed body thereof, and one or more selected from the groupconsisting of a light resisting agent, an ultraviolet absorbent and athermal stabilizer, and additionally the filler sheet is excellent instable adhesiveness to a front face protecting sheet or a rear faceprotecting sheet. Thus, the present invention has been completed.

Accordingly, the present invention relates to a filler sheet for a solarcell module, which is formed as a filler sheet laminated on the frontface and rear face sides of a solar cell element, and is made of a resinfilm produced by a resin composition comprising a copolymer of anα-olefin and an ethylenic unsaturated silane compound, or a modified orcondensed body thereof, and one or more selected from the groupconsisting of a light resisting agent, an ultraviolet absorbent and athermal stabilizer; and a solar cell module using the same.

The present invention also relates to a filler sheet for a solar cellmodule, which is formed as a filler sheet laminated on the front faceand rear face sides of a solar cell element, and is made of a resin filmproduced by a resin composition comprising a maleic anhydride modifiedpolyolefin; and a solar cell module using the same.

The filler sheet according to the present invention which is made of aresin film produced by a resin composition comprising a copolymer of anα-olefin and an ethylenic unsaturated silane compound, or a modified orcondensed body thereof, and one or more selected from the groupconsisting of a light resisting agent, an ultraviolet absorbent and athermal stabilizer is excellent in strength and endurance and furtherexcellent in various properties such as weatherability, heat resistance,water resistance, light resistance, wind pressure resistance, hailstormresistance, and vacuum laminating suitability; and has very good thermalmelting/bonding property without being affected by production conditionsfor heating, compression and others for producing a solar cell module.The use of this filler sheet makes it possible to produce stably a veryuseful solar cell module suitable for various use purposes at low costs.

Furthermore, the filler sheet according to the present invention whichis made of a resin film produced by a resin composition comprising amaleic anhydride modified polyolefin is excellent in the above-mentionedvarious properties. The use of this filler sheet makes it possible toexhibit excellent stable adhesiveness to a surface-treated front faceprotecting sheet or rear face protecting sheet also.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a view which schematically illustrates a layer structure whichis an example of a solar cell module produced by use of a filler sheetaccording to the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail hereinafter.

In the present invention, a sheet means both of a product in a sheetform and a product in a film form, and a film means both of a product ina film form and a product in a sheet form.

[1] Filler Sheet

First, the filler sheet, which is laminated on both of the front sideface and the rear side face of a solar cell element as aphotoelectromotive force element in the present invention, is described.As described above, sunlight is radiated into the filler sheet laminatedon the front face side of the solar cell element, and thus the fillersheet needs to have such a transparency that the sheet transmits thelight. Furthermore, the filler sheet needs to: have adhesiveness to afront face protecting sheet; have thermal plasticity for fulfilling afunction of keeping the smoothness of the front face of the solar cellelement, as a photoelectromotive force element; be excellent in strengthand endurance and further excellent in various properties such asweatherability, heat resistance, light resistance, water resistance,wind pressure resistance, hailstorm resistance, and vacuum laminatingsuitability in order to protect the solar cell element, as aphotoelectromotive force element; have very good thermal melting/bondingproperty without being affected by production conditions for heating,compression and others for producing a solar cell module; and beexcellent in scratch resistance, impact absorptivity, and others.

On the other hand, the filler sheet laminated on the rear face side ofthe solar cell element needs to: have adhesiveness to a rear faceprotecting sheet in the same manner as the filler sheet laminated on thefront face side of the solar element; have thermal plasticity forfulfilling a function of keeping the smoothness of the rear face of thesolar cell element, as a photoelectromotive force element; be excellentin strength and various properties such as weatherability, heatresistance, light resistance, water resistance, wind pressureresistance, hailstorm resistance, and vacuum laminating suitability inorder to protect the solar cell element, as a photoelectromotive forceelement; be very rich in endurance; and be excellent in scratchresistance, impact absorptivity, and others.

However, the filler sheet laminated on the rear face side of the solarcell element may not necessarily have transparency, which is differentfrom the filler sheet laminated on the front face side of the solar cellelement.

As the filler sheet having performances, functions, physical propertiesand others as described above, the following filler sheet is made in thepresent invention: a filler sheet made of a resin film produced by aresin composition comprising a copolymer of an α-olefin and an ethylenicunsaturated silane compound, or a modified or condensed body thereof,and one or more selected from the group consisting of a light resistingagent, an ultraviolet absorbent and a thermal stabilizer (the fillersheet being referred to as the filler sheet (A) as the case may be).

Furthermore, as the filler sheet having performances, functions,physical properties and others as described above, the following fillersheet is made in the present invention: a filler sheet made of a resinfilm produced by a resin composition comprising a maleic anhydridemodified polyolefin (the filler sheet being referred to as the fillersheet (B) as the case may be).

In the present invention, on both of the front side face and the rearside face of a solar cell element, substantially the same material isused to make filler sheets.

Each of the filler sheet (A) and the filler sheet (B) will be describedin detail hereinafter.

1. Filler Sheet (A)

The filler sheet (A) is made of a resin film produced by a resincomposition comprising a copolymer of an α-olefin and an ethylenicunsaturated silane compound, or a modified or condensed body thereof,and one or more selected from the group consisting of a light resistingagent, an ultraviolet absorbent and a thermal stabilizer. The followingwill describe each of the components of this resin composition and aprocess for producing the resin composition.

(1) Copolymer of an α-olefin and an Ethylenic Unsaturated SilaneCompound, or a Modified or Condensed Body Thereof

First, the copolymer of an α-olefin and an ethylenic unsaturated silanecompound, or the modified or condensed body thereof, which constitutesthe filler sheet (A) laminated on both of the front side face and therear face side of a solar cell element in the present invention, isdescribed. This copolymer of an α-olefin and an ethylenic unsaturatedsilane compound, or this modified or condensed body thereof may be, forexample, a product obtained by using a desired reactor torandom-copolymerize one or more α-olefins, one or more ethylenicunsaturated silane compounds and one or more optional other unsaturatedmonomers simultaneously or step by step, for example, at a pressure of500 to 4000 kg/cm², preferably 1000 to 4000 kg/cm² and a temperature of100 to 400° C., preferably 150 to 350° C. in the presence of a radicalpolymerization initiator and an optional chain transfer agent, andfurther modifying or condensing moieties of the silane compound(s)constituting the random copolymer produced by the copolymerization,thereby preparing a copolymer of the α-olefin(s) and the ethylenicunsaturated silane compound(s), or a modified or condensed body thereof.

The copolymer of an α-olefin and an ethylenic unsaturated silanecompound, or the modified or condensed body in the present invention mayalso be, for example, a product obtained by using a desired reactor topolymerize one or more α-olefins and one or more optional otherunsaturated monomers simultaneously or step by step in the presence of aradical polymerization initiator and an optional chain transfer agent inthe same way as described above, next graft-copolymerizing thepolyolefin polymer produced by the polymerization with one or moreethylenic unsaturated silane compounds, or initial condensed products orcondensed products thereof, and further modifying or condensing moietiesof the silane compound(s) constituting the graft copolymer produced bythe copolymerization, thereby preparing a copolymer of the α-olefin(s)and the ethylenic unsaturated silane compound(s), or a modified orcondensed body thereof.

In the copolymer of the α-olefin(s) and the ethylenic unsaturated silanecompound(s), or the modified or condensed body thereof produced asdescribed above, polymer moieties made of the α-olefin(s) are preferablymade of low density polyethylene, linear low density polyethylene, acopolymer made of ethylene and an α-olefin and polymerized by use of asingle site catalyst, or some other polymers from the viewpoint of suchas transparency, working suitability, adhesiveness, and costs.

In the copolymer of the α-olefin(s) and the ethylenic unsaturated silanecompound(s), or the modified or condensed body thereof produced asdescribed above, for example, an alkyl group such as methyl or ethyl, analkoxy group such as methoxy or ethoxy groups, a hydroxyl group, ahalogen atom or some other group may be arbitrary bonded to Si atommoieties constituting the silane compound(s).

As the α-olefin(s) in the above description, for example, one or moreout of the following can be used: ethylene, propylene, 1-butene,isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene,1-heptene, 1-octene, 1-nonene, and 1-decene.

As the ethylenic unsaturated silane compound(s) in the abovedescription, for example, one or more out of the following can be used:vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane,vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane,vinyltriphenoxysilane, vinyltribenzyloxysilane,vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane,vinypropionyloxysilane, vinyltriacetoxysilane, or vinyltricarboxysilane.

As the other unsaturated monomer(s) in the above description, forexample, one or more out of the following can be used: vinyl acetate,acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleicacid, methyl acrylate, methyl methacrylate, ethyl acrylate, styrene,acrylonitrile, methacrylonitrile, or vinyl alcohol.

In the case where the copolymer is modified or condensed in the abovedescription, other silane compounds and so on can be used.

As the radical polymerization initiator in the above description, forexample, the following can be used: an organic peroxide such aslauroylperoxide, dipropionylperoxide, benzoylperoxide,di-t-butylperoxide, t-butylhydroperoxide, t-butylperoxy isobutylate,p-menthanehydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane-3,t-butylperoxy benzoate, dicumylperoxide or2,5-dimethyl-2,5-di(t-butylperoxyhexane), molecular oxygen, or an azocompound such as azobisisobutyronitrile or azoisobutylvaleronitrile.

As the chain transfer agent in the above description, for example, thefollowing can be used: a paraffin hydrocarbon such as methane, ethane,propane, butane or pentane, an α-olefin such as propylene, butene-1, orhexene-1, an aldehyde such as formaldehyde, acetaldehyde, orn-butyraldehyde, a ketone such as acetone, methyl ethyl ketone, orcyclohexanone, an aromatic hydrocarbon, a chlorinated hydrocarbon, orthe like.

The method for modifying or condensing the moieties of the silanecompound(s) constituting the random copolymer or for modifying orcondensing the moieties of the silane compound(s) constituting the graftcopolymer in the above description is, for example, a method of using asilanol condensing catalyst, such as a carboxylate of a metal such astin, zinc, iron, lead or cobalt, an organic metal compound such as anester or chelate compound of titanic acid, an organic base, an inorganicacid, or an organic acid to cause dehydrating condensation reactionbetween silanols in the silane compound moieties constituting the randomcopolymer or graft copolymer of the α-olefin(s) and the ethylenicunsaturated silane compound(s), thereby producing the modified orcondensed body of the α-olefin(s) and the ethylenic unsaturated silanecompound(s).

In the present invention, it is desired that the content of theethylenic unsaturated silane compound(s) constituting the copolymer ofthe α-olefin(s) and ethylenic unsaturated silane compound(s) therein is,for example, from 0.001 to 30% by weight, preferably from 0.01 to 10% byweight, more preferably from 0.01 to 5% by weight.

If the content of the ethylenic unsaturated silane compound(s)constituting the copolymer of the α-olefin(s) and ethylenic unsaturatedsilane compound(s) in the present invention is large, the mechanicalstrength, the heat resistance and others are excellent. However, if thecontent is excessive, the tensile elongation may deteriorate and theethylenic unsaturated silane compound(s) which is/are in a free statebecome(s) one or more adhesion inhibitors to result in a tendency thatthe thermal melting/bonding property is poor. If the content is small,the adhesiveness to the other members may be poor.

In the present invention, the content of the ethylenic unsaturatedsilane compound(s) is most preferably a content as described above inthe material constituting the filler sheet (A) laminated on the frontface side and the rear face side of the solar cell element in order tocause the material to exhibit strength, heat resistance, thermalmelting/bonding property and other effects.

(2) Light Resisting Agent, Ultraviolet Absorbent and Thermal Stabilizer

The following will describe a light resisting agent, an ultravioletabsorbent or a thermal stabilizer which constitutes the filler sheet (A)laminated on the front face side and the rear face side of a solar cellelement in the present invention. The addition of one or more out of thelight resisting agent, the ultraviolet absorbent or the thermalstabilizer in the present invention makes it possible to produce afiller sheet having such as mechanical strength, adhesion strength,anti-yellowing, anti-cracking, excellent work suitability and otherproperties that are stable over a long term.

(Light Resistance Agent)

Firstly, as the light resistance agent, there can be used an agent whichdoes not hinder performances of the filler sheet, such as sealingproperty and transmittance to all rays, and further preventsperformances of the filler sheet from being deteriorated by light. Forexample, a hindered amine type light stabilizer can be used.

Specifically, for example, the following maybe used: N,N′, N″,

N″′-tetrakis(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidine-4-yl)amino)-triazine-2-yl)-4,7-diazadecane-1,10-d iamine, (acondensate of)

dibutylamine-(1,3,5-triazine)-N,N′-bis(2,2,6,6-tetramethyl)-4-piperidyl-1,6-hexamethylenediamine)-N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine,

poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-pyperidyl)imino}],a polymer of dimethyl succinate and

4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, abis(2,2,6,6-tetramethyl-l(octyloxy)-4-piperidinyl) ester of decanedioicacid, a reaction product of

1,1-dimethylethylhydroperoxide and octane,

bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate, a mixture ofbis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and methyl1,2,2,6,6-pentamethyl-4-piperidyl sebacate, or

bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate.

If necessary, these may be used in combination.

It is desired that the added amount thereof, which may be varied inaccordance with the kind of the light resisting agent, is from 0.01 to5% by weight, preferably from 0.01 to 3% by weight, more preferably from0.01 to 1% by weight of the copolymer of the α-olefin and the ethylenicunsaturated silane compound, or the modified or condensed body thereof.

If the amount is less than the above-mentioned range, the effect of thelight resisting agent is insufficient. If the amount is more than therange, the agent may bleed out on the sheet surface to hinder theadhesiveness. Moreover, costs increase. Thus, the case is not preferred.

(Ultraviolet Absorbent)

Secondly, as the ultraviolet absorbent, for example, the following canbe used: an organic compound such as a benzophenone type, benzoate type,triazole type, triazine type, salicylic acid derivative type, oracrylonitrile derivative type compound, or inorganic fine particles madeof titanium oxide, zinc oxide or the like.

Specifically, for example, the following can be used: octabenzone,2-hydroxy-4-n-octoxy-benzophenone, or the like as the benzophenone type,

2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, or the likeas the benzoate type,

2-[5-chloro(2H)-benzotriazole-2-yl]-4-methyl-6-(tert-butyl) phenol,

2,4-di-tert-butyl-6-(5-chlorobenzotriazole-2-yl)phenol, or the like asthe triazole type, or

2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol, or the likeas the triazine type.

If necessary, these may be used in combination.

It is desired that the added amount thereof, which may be varied inaccordance with the kind of the ultraviolet absorbent, is from 0.01 to5% by weight, preferably from 0.01 to 3% by weight, more preferably from0.01 to 1% by weight of the copolymer of the α-olefin and the ethylenicunsaturated silane compound, or the modified or condensed body thereof.

If the amount is less than the above-mentioned range, the effect of theultraviolet absorbent is insufficient. If the amount is more than therange, the agent may bleed out on the sheet surface to hinder theadhesiveness. Moreover, costs increase. Thus, the case is not preferred.

(Thermal Stabilizer)

The thermal stabilizer is used for heat resistance when the resincomposition is worked. There can be used, for example, a phosphorus typethermal stabilizer, a phenol type thermal stabilizer, or a lactone typethermal stabilizer.

Specifically, for example, the following can be used:

tris(2,4-di-tert-butylphenyl) phosphite,

bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphorousacid,

tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4′-diylbisphosphonite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite,or the like as the phosphorus type thermal stabilizer, or a reactionproduct of

3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene, or the like as thelactone type thermal stabilizer.

If necessary, these may be used in combination.

It is desired that the added amount thereof, which may be varied inaccordance with the kind of the thermal stabilizer, is from 0.01 to 5%by weight, preferably from 0.01 to 3% by weight, more preferably from0.01 to 1% by weight of the copolymer of the α-olefin and the ethylenicunsaturated silane compound, or the modified or condensed body thereof.

If the amount is less than the above-mentioned range, the effect of thethermal stabilizer is insufficient. If the amount is more than therange, the agent may bleed out on the sheet surface to hinder theadhesiveness. Moreover, costs increase. Thus, the case is not preferred.

(3) Process for Producing a Resin Composition

The following will describe a process for producing a resin compositioncomprising a copolymer of an α-olefin and an ethylenic unsaturatedsilane compound, or a modified or condensed body thereof, and one ormore of a light resisting agent, an ultraviolet absorbent or a thermalstabilizer in the present invention. Such a resin composition of theinvention can be prepared in the form of pellets, powder or the like byadding one or more light resistance agents, ultraviolet absorbents orthermal stabilizers as described above to one or more copolymers of anα-olefin and an ethylenic unsaturated silane compound, or modified orcondensed bodies thereof, as described above; optionally adding theretoone or more components other than the above-mentioned components at willas long as the advantageous effects of the present invention are notdamaged, specifically adding thereto, for example, various additivesthat are usually used, such as an antioxidant, a nucleating agent, aneutralizing agent, a lubricant, a blocking preventive, an antistaticagent, a dispersing agent, a fluidity improver, a releasing agent, aflame retardant, a colorant and a filler, at will; optionally addingthereto a solvent, a diluting agent or the like; mixing the componentshomogeneously by means of a Henschel mixer, a ribbon blender, a V-shapedblender or the like; and melting and kneading the mixture with auniaxial or multi axial extruder, a roll, a Banbury mixer, a kneader, aBrabender, or the like. The content of the copolymer of the α-olefin andthe ethylenic unsaturated silane compound, or the modified or condensedbody thereof in the resin composition is preferably 0.01% or more byweight, more preferably 1% or more by weight, even more preferably 3% ormore by weight.

In the present invention, a different resin may be added to theabove-mentioned resin composition as long as the invention is notdamaged, thereby preparing a resin composition.

As the above-mentioned resin, for example, an ethylene-α-olefincopolymer polymerized by use of a metallocene catalyst can be used.However, a substance in which the molecular weight distribution of thepolymer as a main polymer is narrow in this manner is somewhat poor inmoldability. It is therefore possible to use low density polyethylene,polypropylene or the like which has a different density and add this soas to improve the moldability.

2. Filler Sheet (B)

Next, the filler sheet (B) will be described.

The filler sheet (B) is made of a resin film produced by a resincomposition comprising a maleic anhydride modified polyolefin, and oneor more of a light resisting agent, an ultraviolet absorbent or athermal stabilizer. The following will describe each component of thisresin composition and a process for producing the resin composition.

(1) Maleic Anhydride Modified Polyolefin

The maleic anhydride modified polyolefin which is used in the presentinvention and constitutes the filler sheet (B) laminated on both of thefront side face and the rear side face of a solar cell element is asubstance obtained by polymerizing an α-olefin and an optional differentunsaturated monomer to yield a polyolefin polymer, graft-copolymerizingthis polymer with maleic anhydride, and then modifying the resultantcopolymer. The filler sheet (B) is useful since the use of such a maleicanhydride modified polyolefin therein makes the filler sheet (B) rich inreactivity with polar groups present on the surface of a front faceprotecting sheet or a rear face protecting sheet, the surface beingsubjected to surface treatment, so that the sheet (B) can surely keepstable adhesiveness to the protecting sheet. The maleic anhydridemodified polyolefin is profitable from the viewpoint of costs also sincethe polyolefin does not generate any byproducts of low molecular weightcompound in the process of adhesion formation so as not to deteriorateworking environment.

In the filler sheet (B) of the present invention, only one kind of themaleic anhydride modified polyolefin may be used, or two or more kindsof maleic anhydride modified polyolefins may be used together.

Such a maleic anhydride modified polyolefin can be produced by using adesired reactor to polymerize one or more α-olefins and optional one ormore different unsaturated monomers simultaneously or step by step, forexample, at a pressure of usually 500 to 4000 kg/cm², preferably 1000 to4000 kg/cm² and a temperature of usually 100 to 400° C., preferably 150to 350° C. in the presence of a radical polymerization initiator and anoptional chain transfer agent; and next graft-copolymerizing thepolyolefin polymer produced by the polymerization with maleic anhydride.

Examples of the α-olefin (s) used in the present invention includeethylene, propylene, 1-butene, isobutylene, 1-pentene,2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 1-heptene,4-methylpentene-1,1-octene, 1-nonene, 1-decene and the like.

Preferred examples of polymer moieties made of the one or more α-olefinsinclude low density polyethylene, middle density polyethylene, highdensity polyethylene, super low density polyethylene, linear low densitypolyethylene, polypropylene, and a copolymer made of ethylene and anα-olefin and polymerized by use of a single site catalyst from theviewpoint of transparency, working suitability, adhesiveness, costs, andothers.

Of these, linear low density polyethylene is particularly preferredsince it has a narrow molecular weight distribution so as not toproduce, as a by product, a low molecular weight compound originatingfrom a low molecular weight polymer in the process of adhesionformation.

As the different unsaturated monomer(s) optionally used in theabove-mentioned polyolefin polymer, the radical polymerization initiatorand the chain transfer agent, the same as described about the fillersheet (A) can be used.

The maleic anhydride modified polyolefin used in the present inventionis a substance obtained by graft-copolymerizing a polyolefin polymer asdescribed above with maleic anhydride and then modifying the resultant.In the invention, the content ratio of maleic anhydride in this maleicanhydride modified polyolefin is preferably from 0.001 to 30% by weight,more preferably from 0.01 to 10% by weight, even more preferably from0.01 to 5% by weight.

A case in which the content ratio of maleic anhydride is large ispreferred for the following reason: even in the case of using, as afront face protecting sheet, a material poor in adhesiveness such as afluorine-contained resin sheet subjected to atmospheric pressure plasmatreatment or using, as a rear face protecting sheet, a material poor inadhesiveness such as a color steel plate painted with polyester paint,the filler sheet can be bonded strongly to functional groups on thesurface thereof to keep adhesive stability surely. However, if thecontent ratio of maleic anhydride is too large, the production of anunreacted product or a by product cannot be controlled to give a lowadhesive performance.

In the present invention, the weight-average molecular weight of such amaleic anhydride modified polyolefin is preferably from 1,000 to1300,000, more preferably from 10,000 to 500,000, even more preferablyfrom 50,000 to 100,000 as obtained by gel permeation chromatography. Ifthe molecular weight is lower than this range, the production of anunreacted product or a byproduct cannot be controlled to give a lowadhesive performance. Conversely, if the molecular weight is higher thanthis range, the transparency deteriorates.

The ratio of the weight-average molecular weight (Mw) to thenumber-average molecular weight (Mn), (Mw/Mn), is preferably 6 or less,more preferably 5 or less, even more preferably 4 or less. When theratio is within this range, the generation of a byproduct, resultingfrom a low molecular weight polymer, is restrained since the dispersionof the molecular weight distribution is narrow.

In the present invention, the number-average molecular weight (Mn) canbe obtained from a molecular weight distribution chart obtained byseparating molecules of the polymer based on a difference in moleculesize by gel permeation chromatography.

(2) Light Resisting Agent, Ultraviolet Absorbent and Thermal Stabilizer

The resin film constituting the filler sheet (B) of the invention ispreferably a resin film obtained by use of a resin compositioncomprising the above-mentioned maleic anhydride modified polyolefin andadditionally one or more of a light resistance agent, an ultravioletabsorbent or a thermal stabilizer. As such a light resistance agent,ultraviolet absorbent or thermal stabilizer which is used in the fillersheet (B), the same as described about the filler sheet (A) can be used.The used amount thereof is preferably within a similar range.

(3) Process for Producing a Resin Composition

The following will describe a process for producing a resin compositioncomprising a maleic anhydride modified polyolefin and one or more of alight resisting agent, an ultraviolet absorbent or a thermal stabilizer.Such a resin composition of the invention can be prepared in the form ofpellets, powder or the like by adding one or more light resistanceagents, ultraviolet absorbents or thermal stabilizers as described aboveto one or more maleic anhydride modified polyolefins as described above;optionally adding thereto one or more components other than theabove-mentioned components at will as long as the advantageous effectsof the present invention are not damaged, specifically adding thereto,for example, various additives that are usually used, such as anantioxidant, a nucleating agent, a neutralizing agent, a lubricant, ablocking preventive, an antistatic agent, a dispersing agent, a fluidityimprover, a releasing agent, a flame retardant, a colorant and a filler,at will; optionally adding thereto a solvent, a diluting agent or thelike; mixing the components homogeneously by means of a Henschel mixer,a ribbon blender, a V-shaped blender or the like; melting and kneadingthe mixture with a uniaxial or multi axial extruder, a roll, a Banburymixer, a kneader, a Brabender, or the like. The content of the maleicanhydride modified polyolefin in the resin composition is preferably0.01% or more by weight, more preferably 1% or more by weight, even morepreferably 3% or more by weight.

In the present invention, a different resin may be added to theabove-mentioned resin composition as long as the invention is notdamaged, thereby preparing a resin composition. It is preferred to use,as the different resin, low-density polyethylene, polypropylene or thelike which has a different density for improving the moldability for thesame reason as described about filler sheet (A).

3. Process for Producing a Filler Sheet

The following will describe a process of using a resin compositioncomprising a copolymer of an α-olefin and an ethylenic unsaturatedsilane compound, or a modified or condensed body thereof, and one ormore of a light resisting agent, an ultraviolet absorbent or a thermalstabilizer, or a resin composition comprising a maleic anhydridemodified polyolefin and one or more of a light resisting agent, anultraviolet absorbent or a thermal stabilizer in the present inventionto form a filler sheet made of a resin film produced by thiscomposition. Examples of such a process include a process of using theresin composition, prepared as described above, according to theinvention and molding the resin composition according to the inventioninto a film or sheet by a molding method that is ordinarily used forordinary thermoplastic resin, that is, any one of various moldingmethods such as injection molding, extrusion molding, hollow molding,compression molding and rotational molding, and then producing a fillersheet using the film or sheet as a resin film.

The case that the resin composition is used in the form of a masterbatch in the invention and then this is incorporated/molded is preferredsince the composition is excellent in dispersibility, moldability andothers.

In the present invention, a solar cell module can be produced by using afilm or sheet made of the resin composition according to the presentinvention; and using an ordinary molding process “such as a laminationprocess of laminating a front face protecting sheet, the film or sheetas a filler layer, a solar cell element as a photoelectromotive forceelement, the film or sheet as a filler layer, and a rear face protectingsheet in sequence, and next integrating these layers by vacuum suctionor the like to heat and compress the layers” to heat, compress and moldthe respective layers into an integrated molded body.

Alternatively, in the present invention, the resin composition accordingto the invention is used, and the resin composition according to theinvention is melted, extruded and laminated onto the front face of asolar cell element and the rear face thereof by a molding processordinarily used for ordinary thermoplastic resin, that is, by any one ofvarious processes such as a T-die extrusion molding, so as to formextruded resin layers made of the resin composition according to theinvention on the front face and the rear face of the solar cell element,thereby making it possible to make a filler sheet in which the extrudedresin layers are resin films.

In other words, in the present invention, a solar cell module can beproduced by using the resin composition according to the invention;melting, extruding and laminating this onto the front face and the rearface of a solar cell element to form extruded resin layers; and nextusing an ordinary molding process “such as a lamination process oflaminating a front protecting sheet, the solar cell element having, onits front face and its rear face, the extruded resin layers as fillerlayers, and a rear face protecting sheet in sequence, and nextintegrating these layers by vacuum suction or the like to heat andcompress the layers” to heat, compress and mold the respective layersinto an integrated molded body.

Furthermore, in the present invention, the resin composition of theinvention is used, and the resin composition according to the inventionis melted, extruded and laminated onto the front faces of a front faceprotecting sheet and a rear face protecting sheet by a molding processordinarily used for ordinary thermoplastic resin, that is, by any one ofvarious processes such as a T-die extrusion molding, so as to formextruded resin layers made of the resin composition according to theinvention on the surface of each of the front face protecting sheet andthe rear face protecting sheet, thereby making it possible to make afiller sheet in which the extruded resin layers are resin films.

In other words, in the present invention, a solar cell module can beproduced by using the resin composition according to the invention;melting, extruding and laminating this on the surface of each of a frontface protecting sheet and a rear face protecting sheet to form extrudedresin layers; and next using an ordinary molding process “such as alamination process of laminating the front face protecting sheet, theextruded resin layer as a filler sheet laminated on the surface of theprotecting sheet, a solar cell element, the extruded resin layer as afiller sheet laminated on the surface of the rear face protecting sheet,and the rear face protecting sheet in sequence and next integratingthese layers by vacuum suction or the like to heat and compress thelayers” to heat, compress and mold the above-mentioned respective layersinto an integrated molded body.

Moreover, in the present invention, a solar cell module can be producedby forming a p layer, an i layer, an n layer and so on, which constitutean amorphous silicon solar cell element, on the surface of a glasssubstrate as a front face protecting sheet; next melting, extruding andlaminating the resin composition according to the present invention ontothe surface of the amorphous silicon solar cell element formed asdescribed above to form an extruded resin layer as a filler sheet; andusing an ordinary molding process “such as a lamination process oflaminating a rear face protecting sheet on the face of the extrudedresin layer, and next integrating these layers by vacuum suction or thelike to heat and compress the layers” to heat, compress and mold theabove-mentioned respective layers into an integrated molded body.

In the present invention, it is preferred that the film thickness of thefiller sheet made of the resin film produced by the resin compositionaccording to the present invention is from 100 μm to 1 mm, preferablyfrom 300 μm to 600 μm.

The filler sheet made of the resin film produced by the resincomposition according to the present invention exhibits thermalmelting/bonding property and so on by heating and compression performedwhen a solar cell module is molded, and makes it possible to produce asolar cell module very good in endurance by laminating a front faceprotecting sheet, the above-mentioned film or sheet as a filler sheet, asolar cell element as a photoelectromotive force element, theabove-mentioned film or sheet as a filler sheet, and a rear faceprotecting sheet in sequence and further thermally melting/bonding thesemembers.

The filler sheet made of the resin film produced by the resincomposition according to the present invention does not undergophenomena that the sheet itself receives effect by action of heat and soon so that the structure and the like thereof breaks or decomposes.Accordingly, the generation of decomposition gas, impurities and so on,which follows the breakdown, decomposition or the like, is notrecognized, and this does not produce a bad effect onto a solar cellelement and so on. Thus, a solar cell modulus very good in endurance canbe produced.

Furthermore, the filler sheet made of the resin film produced by theresin composition according to the present invention is excellent instrength and endurance, is also excellent in various properties such asweatherability, heat resistance, light resistance, water resistance,wind pressure resistance and hailstorm resistance, and is furtherexcellent in scratch resistance and impact absorptivity. Accordingly, asolar cell modulus very good in endurance can be produced.

The gel fraction in the filler sheet for a solar cell module of thepresent invention is preferably 10% or less, in particular preferably0%. If the gel fraction is over this range, the workability thereof maylower or the adhesion thereof to a front face protecting sheet or rearface protecting sheet may become insufficient when a solar cell moduleis produced. The gel fraction in the filler sheet is the gel fraction inthe exfoliation layer at the time of producing a solar cell module byusing an ordinary molding process “such as a lamination process oflaminating, for example, a front face protecting sheet, the fillersheet, a solar cell element, the filler sheet and a rear face protectingsheet in this order, and then integrating, heating and compressing theselayers while vacuum-sucking the layers” to integrate the respectivelayers into a molded body.

[2] Solar Cell Module

The following will describe a solar cell module according to the presentinvention produced by use of a filler sheet made of a resin filmobtained by the resin composition according to the present invention.

First, a drawing and so on are used to illustrate a layer structure of asolar cell module according to the present invention produced by use ofa filler sheet made of a resin film obtained by the resin compositionaccording to the present invention. FIG. 1 is a schematic sectional viewillustrating an example of the layer structure of the solar cell moduleaccording to the invention.

As illustrated in FIG. 1, the solar cell module 10 according to theinvention has, as a basic structure, a structure obtained by using anordinary molding process “such as a lamination process of laminating afront face protecting sheet 1, a filler sheet 2, a solar cell element 3as a photoelectromotive force element, a filler sheet 4, and a rear faceprotecting sheet 5 in sequence, and next heating and compressing theselayers while vacuum-sucking the layers” to integrate the respectivelayers into a molded body.

The above-mentioned illustration shows an example of the solar cellmodule according to the present invention, and the present invention isnot limited by this.

For example, a different substrate and the like for the absorption ofsunlight, reinforcement and others are arbitrarily added to theabove-mentioned solar cell module so as to be laminated and integratedso that a solar cell module can be produced, which is not illustrated.The following will describe the respective layers of the solar cellmodule according to the present invention in detail.

1. Front Face Protecting Sheet

In the above description, the front face protecting sheet whichconstitutes the solar cell module according to the present inventiondesirably has various properties such as that the sheet hastransmittance of sunlight and electric insulation and is excellent inmechanical, chemical and physical strengths, specifically, the sheet isexcellent in various resistance properties such as weatherability, heatresistance, water resistance, light resistance, wind pressureresistance, hailstorm resistance and chemical resistance, in particularlight resistance, is excellent in moisture proof property of preventingthe invasion of water, oxygen and the like, is high in surface hardness,is excellent in antifouling property of preventing surface contaminationand accumulation of dust, is very rich in endurance, and has a highprotecting capability.

In the invention, as a front face protecting sheet as described above,specifically, the following can be used: for example, films or sheetmade of various resins such as polyethylene resins, polypropyleneresins, cyclic polyolefine resins, fluorine-contained resins,polystyrene resins, acrylonitrile-styrene copolymers (AS resins),acrylonitrile-butadiene-styrene copolymers (ABS resins), polyvinylchloride resins, poly(meth)acrylic resins, polycarbonate resins,polyester resins such as polyethylene terephthalate and polyethylenenaphthalate, polyamide resins such as various nylons, polyimide resins,polyamideimide resins, polyaryl phthalate resins, silicone resins,polysulfone resins, polyphenylenesulfide resins, polyethersulfoneresins, polyurethane resins, acetal resins, and cellulose resins, aswell as a glass plate.

It is particularly preferred to use, out of the above-mentioned resinfilms or sheets, films or sheets of fluorine-contained resins, cyclicpolyolefine resins, polycarbonate resins, poly(meth)acrylic resins, orpolyester resins in the invention.

Thus, in the invention, the films or sheets of fluorine-containedresins, cyclic polyolefine resins, polycarbonate resins,poly(meth)acrylic resins, or polyester resins as described above haveadvantages such that the films or sheets are excellent in mechanical,chemical and physical properties, specifically, excellent in variousresistance properties such as weatherability, heat resistance, waterresistance, light resistance, moisture proof property, antifoulingproperty and chemical resistance, are light based on the flexibility,mechanical property and chemical property thereof, are excellent inworkability, and are easy to handle.

It is particularly preferred in the invention to use, out of variousresin films or sheets as described above, fluorine-contained resinsheets made of polyvinyl fluoride resins (PVF) or copolymers oftetrafluoroethylene and ethylene or propylene (ETFE), or cyclicpolyolefine resin sheets made of cyclic diene polymers or copolymerssuch as cyclopentadiene and derivatives thereof, dicyclopentadiene andderivatives thereof, or norbornadiene and derivatives thereof.

Thus, in the invention, the use of fluorine-contained resin sheets orcyclic polyolefine resin sheets as described above is permitted to useexcellent properties such as mechanical, chemical and physicalproperties they have, specifically various properties such asweatherability, heat resistance, water resistance, light resistance,moisture proof property, antifouling property and chemical resistance,thereby preparing the front face protecting sheet constituting a solarcell module. This causes the solar cell module to have advantages suchthat the module has endurance and a protecting function, is light basedon the flexibility, mechanical property and chemical property thereof,is excellent in workability, and is easy to handle.

About the front face protecting sheet used in the invention, it ispreferred to dispose a surface-treated layer on the above-mentionedvarious resin films or sheets in order to improve the adhesion of thefront face protecting sheet to the filler sheet.

Such a surface-treated layer can be disposed by conducting apre-treatment, such as corona discharge treatment, ozone treatment,low-temperature plasma treatment with oxygen gas, nitrogen gas or thelike, glow discharge treatment, or oxidation treatment with a chemicalor the like, at will so as to form, for example, a corona-treated layer,an ozone-treated layer, a plasma-treated layer, or oxidized layer. Ofthese, the plasma-treated layer is particularly preferred since gas forthe treatment can be selected at will under atmospheric pressure so thata polymer surface can freely be constructed.

It is particularly preferred to use, as the front face protecting sheetof the invention, a front face protecting sheet in which afluorine-contained resin sheet as described above is used as a substrateand the above-mentioned surface-treated layer, in particular theplasma-treated layer, is disposed thereon. Such a front face protectingsheet has an excellent transparency, a good weatherability, a largemechanical strength, an excellent chemical resistance and stability overa wide temperature range; therefore, excellent in heat resistance andcan satisfy required properties such as water resistance, lightresistance, moisture proof property and antifouling property.

In the case where the surface-treated layer is disposed on the frontface protecting sheet, it is preferred to use, as the filler sheet, thefiller sheet (B) of the invention. This is because a maleic anhydridemodified polyolefin, which is a constituent material of the filler sheet(B), reacts with polar groups present on the surface-treated layer tokeep adhesive stability surely in the interface between the front faceprotecting sheet and the filler sheet.

In the invention, it is possible to use, as any one of various resinfilms or sheets, for example, a film or sheet obtained by: using one ormore of the above-mentioned various resins and further using afilm-forming process, such as an extrusion, cast molding, T-die, cuttingor inflation process, to produce the resin film or sheet by a process offorming only one of the various resins into a film, a process of usingtwo or more of the various resins so as to be co-extruded into amulti-layered film, a process of using two or more of the resins, mixingthe resins before film-formation, and subsequently forming the mixtureinto a film, or some other process; and optionally using, for example, atenter manner or a tubular manner to draw the resultant film or sheetuni-axially or bi-axially.

In the invention, the film thickness of the various resin films orsheets is desirably from 6 to 300 μm, more preferably from 9 to 150 μm.

In the invention, it is desired that the various resin films or sheetshave a visible ray transmittance of 90% or more, preferably 95% or moreand have a nature that the films or sheets transmit all of incidentsunlight rays. In the invention, the visible ray transmittance can bemeasured with a color computer.

When one or more of the above-mentioned various resins are used to forma film, it is possible to add thereto various plastic compounding agentsor additives for improving or modifying the workability, heatresistance, weatherability, mechanical property, dimensional stability,antioxidation, lubricity, releasing property, flame resistance, fungusresistance, electric property, strength and so on of the film. The addedamount thereof is any value from an extremely small amount to severaltens of percentages dependently on the purpose thereof.

In the above description, ordinary examples of the additives which canbe used include a lubricant, a crosslinking agent, an antioxidant, anultraviolet absorbent, a light stabilizer, a filler, a reinforcingfiber, a reinforcing agent, an antistatic agent, a flame retardant, aflame resisting agent, a foaming agent, an antifungal agent, and apigment. A reforming resin and the like can also be used.

Thus, in the invention, it is particularly preferred to use the variousresin films or sheets into which one or more of the ultravioletabsorbent, antioxidant or reinforcing fiber out of the above-mentionedadditives are kneaded in order to improve the weatherability, stickingresistance and others.

The ultraviolet absorbent is an agent for absorbing harmful ultravioletrays out of sunlight and converting the rays into thermal energynonpoisonous inside molecules to prevent active species for opticaldeterioration start in a polymer from being excited. For example, thefollowing can be used: one or more inorganic or organic ultravioletabsorbents such as benzophenone based, benzotriazole based, salicylatebased, acrylonitrile based, metallic complex salt based, and hinderedamine based compounds, and ultra fine particle titanium oxide (particlesize: 0.01 to 0.06 μm) or ultra fine particle zinc oxide (particle size:0.01 to 0.04 μm).

The antioxidant is an agent for preventing optical deterioration,thermal deterioration or the like of a polymer. For example, a phenoltype, an amine type, a sulfur type, or a phosphoric acid typeantioxidant can be used.

It is possible to use, as the above-mentioned ultraviolet absorbent orantioxidant, for example, a polymer type ultraviolet absorbent orantioxidant in which the above-mentioned ultraviolet absorbent, such asthe benzophenone based absorbent, or the above-mentioned antioxidant,such as the phenol type antioxidant, is chemically bonded to a mainchain or side chains which constitute a polymer.

It is possible to use, as the reinforcing fiber, for example, glassfiber, carbon fiber, aramide fiber, polyamide fiber, polyester fiber,polypropylene fiber, polyacrylonitrile fiber or natural fiber. The fibercan be used in a long or short fiber form or in a woven fabric cloth ornonwoven fabric cloth form.

The content of the ultraviolet absorbent, the antioxidant, thereinforcing fiber, or the like is varied by the particle form thereof,the density thereof or the like, and is preferably from 0.1 to 10% byweight.

2. Solar Cell Element

The following will describe the solar cell element, as aphotoelectromotive force element, which constitutes the solar cellmodule in the present invention. As such a solar cell element, any onethat is ordinarily used can be used, examples of which include crystalsilicon solar cell elements such as a monocrystal silicon type solarcell element and a polycrystal silicon type solar cell element; singlejoint type, tandem structure type, and other type amorphous siliconsolar cell elements; gallium arsenide (GaAs), indium phosphorus (InP),and other III-V group compound semiconductor solar cell elements; andcadmium tellurium (CdTe), copper indium selenide (CuInSe₂), and otherII-VI group compound semiconductor solar cell elements.

Furthermore, there can be used a thin film polycrystalline silicon solarcell element, a thin film microcrystalline silicon solar cell element,or a hybrid element of a thin film crystal silicon solar cell elementand an amorphous silicon solar cell element.

In the invention, the solar cell element is constructed by forming anelectromotive force region such as crystal silicon having a pn junctionstructure or the like, amorphous silicon having a p-i-n junctionstructure or the like, or a compound semiconductor on a substrate suchas a glass substrate, a plastic substrate or a metal substrate.

3. Rear Face Protecting Sheet

The following will describe the rear face protecting sheet whichconstitutes the above-mentioned solar cell module in the invention. Sucha rear face protecting sheet needs to have weatherability such as heatresistance, light resistance and water resistance, is excellent inphysical or chemical strength and toughness, and is further excellent inscratch resistance, impact absorptivity and soon for protecting thesolar cell element as a photoelectromotive force element.

The rear face protecting sheet may not have necessarily suchtransparency as the above-mentioned front face protecting sheet has, andmay or may not have transparency.

Thus, in the invention, as the rear face protecting sheet, for example,an insulating resin film or sheet can be used. Basically, the variousresin films or sheets illustrated about the above-mentioned front faceprotecting sheet can be used in the same manner.

In the invention, as the rear face protecting sheet, specifically, thefollowing can be used: for example, films or sheets made of variousresins such as polyethylene resins, polypropylene resins, cyclicpolyolefine resins, fluorine-contained resins, polystyrene resins,acrylonitrile-styrene copolymers (AS resins),acrylonitrile-butadiene-styrene copolymers (ABS resins), polyvinylchloride resins, poly(meth)acrylic resins, polycarbonate resins,polyester resins such as polyethylene terephthalate and polyethylenenaphthalate, polyamide resins such as various nylons, polyimide resins,polyamideimide resins, polyaryl phthalate resins, silicone resins,polysulfone resins, polyphenylenesulfide resins, polyethersulfoneresins, polyurethane resins, acetal resins, and cellulose resins.

It is particularly preferred to use, out of the above-mentioned resinfilms or sheets, films or sheets of fluorine-contained resins, cyclicpolyolefine resins, polycarbonate resins, poly(meth)acrylic resins, orpolyester resins in the invention.

Thus, in the invention, the films or sheets of fluorine-containedresins, cyclic polyolefine resins, polycarbonate resins,poly(meth)acrylic resins, or polyester resins as described above haveadvantages such that the films or sheets are excellent in mechanical,chemical and physical properties, specifically, excellent in variousresistance properties such as weatherability, heat resistance, waterresistance, light resistance, moisture proof property, antifoulingproperty and chemical resistance, are useful as protecting sheetsconstituting solar cells, are excellent in endurance and protectingfunction property, are light based on the flexibility, mechanicalproperty and chemical property thereof, are excellent in workability,and are easy to handle.

It is particularly preferred in the invention to use, out of variousresin films or sheets as described above, for example, theabove-mentioned fluorine-contained resin sheets, in particularfluorine-contained resin sheets made of polyvinyl fluoride resins (PVF)or copolymers of tetrafluoroethylene and ethylene or propylene (ETFE),or cyclicpolyolefine resin sheets, in particular cyclic polyolefineresin sheets made of cyclopentadiene and derivatives thereof,dicyclopentadiene and derivatives thereof, or norbornadiene andderivatives thereof in the same manner as in the above-mentioned frontface protecting sheet.

Thus, in the invention, the use of fluorine-contained resin sheets orcyclic polyolefine resin sheets as described above is permitted to useexcellent properties such as mechanical, chemical and physicalproperties they have, specifically various properties such asweatherability, heat resistance, water resistance, light resistance,moisture proof property, antifouling property and chemical resistance,thereby preparing the rear face protecting sheet constituting a solarcell module. This causes the solar cell module to have advantages suchthat the module has endurance and a protecting function, is light basedon the flexibility, mechanical property and chemical property thereof,is excellent in workability, and is easy to handle.

In the invention, about the above-mentioned various resin films orsheets, it is permissible in the same manner as about the front faceprotecting sheet that various resin films or sheets are produced andoptionally these are further drawn uni-axially or bi-axially.

When one or more of the above-mentioned various resins are used andformed into a film, various plastic compounding agents or additives canbe added thereto in the same manner as about the front face protectingsheet.

In the same manner as about the front face protecting sheet, it ispreferred to use the various resin films or sheets into which one ormore of an ultraviolet absorbent, antioxidant or reinforcing fiber outof the above-mentioned additives are kneaded in order to improve theweatherability, sticking resistance and others.

As the above-mentioned ultraviolet absorbent, one or more inorganic ororganic ultraviolet absorbents can be used in the same manner asdescribed above. As the above-mentioned antioxidant, a phenol type, anamine type, a sulfur type, a phosphorus type or some other typeantioxidant can be used in the same manner as described above. It ispossible to use, as the above-mentioned ultraviolet absorbent orantioxidant, for example, a polymer type ultraviolet absorbent orantioxidant in which the above-mentioned ultraviolet absorbent, such asthe benzophenone based absorbent, or the above-mentioned antioxidant,such as the phenol type antioxidant, is chemically bonded to a mainchain or side chains which constitute a polymer.

It is possible to use, as the reinforcing fiber, for example, glassfiber, carbon fiber, aramide fiber, polyamide fiber, polyester fiber,polypropylene fiber, polyacrylonitrile fiber or natural fiber in thesame manner as described above. The fiber can be used in a long or shortfiber form or in a woven fabric cloth or nonwoven fabric cloth form.

The film thickness of the above-mentioned resin films or sheets isdesirably from 12 to 200 μm, more preferably from 25 to 150 μm.

In the invention, it is possible to use, as the rear face protectingsheet constituting the solar cell module, a laminate material made byusing two or more kinds of resin films or sheets as described above andlaminating them through one or more adhesive agent layers or the like, alaminate material made by laminating a metal foil such as aluminum foilon the above-mentioned resin film or sheet, a metal plate, or a resinfilm or sheet made by coloring or decorating the above-mentioned resinfilm or sheet with a coloring agent such as dye or pigment, consideringthe decorative or designable property of the rear face of the solar cellmodule.

It is preferred in the invention to use, as a member satisfying therequired properties of the above-mentioned rear face protecting sheet,the so-called color steel plate, which has a front face on which apainted film is formed.

The steel plate as the original plate of the color steel plate is notparticularly limited if the steel plate is ordinarily used in a colorsteel plate. It is preferred to use a galvanium steel plate, where steelis covered with an alloy of zinc and aluminum, since the plate isexcellent in corrosion resistance, workability, heat resistance, heatreflectivity, endurance, and sacrificial rust-proofing effect onto iron.

The painted film is not particularly limited if the painted film can beformed as an insulator film on the steel plate to give corrosionresistance and decorative property thereto. For example, afluorine-contained resin painted film or a polyester painted film can bepreferably used since the fluorine-contained resin painted film isexcellent in antifouling property, chemical resistance, corrosionresistance and heat resistance and the polyester painted film isexcellent in corrosion resistance and is inexpensive.

When a color steel plate as described above is used as the rear faceprotecting sheet, it is preferred to use, as the filler sheet, thefiller sheet (B) of the invention since the filler sheet (B) can react,because of the use of a maleic anhydride modified polyolefin therein,with polar groups present on the surface of such a painted film, so asto keep surely highly stable adhesiveness to the painted film.

In the invention, the above-mentioned film or sheet can be used in anyone of non-drawn form, uni-axially or bi-axially drawn forms, and otherforms.

The thickness thereof is selected at will, and can be selected from therange of several micrometers to 3 mm.

In the invention, the film or sheet may be any one of an extruded film,an inflation film, a coating film and other films.

4. Other Materials

When the solar cell module according to the invention is produced in theinvention, a material selected at will from the following can be used inorder to improve the strength thereof and various resistances thereof,such as weatherability and scratch resistance thereof: other materials,for example, films or sheets made of ordinarily used resins, such as lowdensity polyethylene, middle density polyethylene, high densitypolyethylene, straight chain low density polyethylene, polypropylene,ethylene-propylene copolymers, ethylene-vinyl acetate copolymers,ionomer resins, ethylene-ethyl acrylate copolymers, ethylene-acrylic ormethacrylic acid copolymers, methylpentene polymers, polybutene resins,polyvinyl chloride resins, polyvinyl acetate resins, polyvinylidenechloride resins, vinyl chloride-vinylidene chloride copolymers,poly(meth)acrylic resins, polyacrylonitrile resins, polystyrene resins,acrylonitrile-styrene copolymer (AS resins),acrylonitrile-butadiene-styrene copolymers (ABS resins), polyesterresins, polyamide resins, polycarbonate resins, polyvinyl alcoholresins, saponified ethylene-vinyl acetate copolymers, fluorine-containedresins, diene resins, polyacetal resins, polyurethane resins, andnitrocellulose.

5. Process for Producing the Solar Cell Module

The following will describe a process for producing, in the invention,the solar cell module according to the invention. An example of such aproducing process is a process of using an ordinarily used process “suchas a lamination process of facing a front face protecting sheet, afiller sheet according to the invention, a solar cell element as aphotoelectromotive force element, a filler sheet according to theinvention, and a rear face protecting sheet, laminating them insequence, optionally laminating other materials between the respectivelayers at will, and next integrating these layers by vacuum-suction orthe like to heat and compress the layers” to heat and compress therespective layers into an integrated molded body, thereby producing thesolar cell module according to the invention. In this process, it ispermissible to use a member in which a front face protecting sheet and afiller sheet are beforehand laminated so as to be integrated, or amember in which a rear face protecting sheet and a filler sheet arebeforehand laminated so as to be integrated.

In the above description, in order to make the adhesiveness or the likebetween the respective layers high, the following can be used ifnecessary: a hot melt type adhesive agent, a solvent type adhesiveagent, a photo curing adhesive agent or the like the vehicle of which ismade mainly of a resin such as (meth)acrylic resin, olefin resin, orvinyl resin.

In order to improve the adhesion between laminating and facing faces inthe above-mentioned lamination, a pre-treatment can be applied to eachof the faces at will if necessary, examples of the treatment includingcorona discharge treatment, ozone treatment, low-temperature plasmatreatment with oxygen gas, nitrogen gas or the like, glow dischargetreatment, and oxidation treatment with a chemical or the like.

In the above-mentioned lamination, a surface pre-treatment can beconducted by forming, onto each of the laminating and facing faces, aprimer coating agent layer, an undercoating agent layer, an adhesiveagent layer, an anchor coating agent layer or the like in advance atwill.

As the coating agent layer for the pre-treatment, there can be used, forexample, a resin composition the vehicle of which is made mainly of apolyester resin, polyamide resin, polyurethane resin, epoxy resin,phenol resin, (meth)acrylic resin, polyvinyl acetate resin or polyolefinresin such as polyethylene or polypropylene, a copolymer or modifiedpolymer thereof, a cellulose resin, or the like.

In the above description, examples of the method for forming the coatingagent layer include roll coating, gravure roll coating, and kiss coatingby use of a solvent type, aqueous type or emulsion type coating agent.

In the solar cell module according to the invention, the materialconstituting its filler sheet can be stably produced at low costswithout being affected by such as conditions for producing the solarcell module, thereby making it possible to render this module a solarcell module excellent in strength and various properties such asweatherability, heat resistance, water resistance, light resistance,wind pressure resistance and hailstorm resistance, and very rich inendurance.

Thus, the solar cell according to the invention is suitable for varioususe purposes, and is used in, for example, a crystal silicon solar cellelement, an amorphous solar cell element, a solar cell set on a houseroof, which is widely and generally used on the ground, or a solar cellembedded in a house roof, which is of a roof member type.

The amorphous solar cell element can be used in a wrist watch, acalculator or the like for the people's livelihood, and is very useful.

The present invention is not limited to the above-mentioned embodiments.The embodiments are examples, and all products having substantially thesame structure as the technical concept described in the claims of theinvention and producing the same effect and advantages are included inthe invention.

EXAMPLES

The present invention will be more specifically described by way ofexamples hereinafter.

Example 1

(1) Production of a Filler Sheet (A)

Three parts by weight of vinyltrimethoxysilane and 0.1 part by weight ofa free radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%. With 85 parts by weight of the resultantpolyethylene were mixed 2.5 parts by weight of a hindered amine typelight stabilizer, 7.5 parts by weight of a benzophenone type ultravioletabsorbent and 5 parts by weight of a phosphorus type thermal stabilizer,and then the mixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 3 parts by weight of the master batch, and thena film-forming machine having an extruder 25 mm in diameter and a T die300 mm in width was used to form the resin into a film 400 μm inthickness at a resin temperature of 230° C. and a pulling-out rate of 3m/minute.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength thereof to a frontface protecting sheet, a rear face protecting sheet and a solar cellelement (cell), the film was not easily peeled and was in a good stateeven after the module was allowed to stand in a state of ahigh-temperature of 85° C. and a high-humidity of 85% for 1000 hours.Even after the module was subjected to a sunshine weatherometer test(sunshine carbon arc lamp illuminance: 255 W/m², temperature: 60° C.,and humidity: 60%) for 500 hours, the film was not easily peeled and wasin a good state.

(2) Production of a Solar Cell Module

The above-mentioned produced film was used as a filler sheet, and thefollowing were laminated through acrylic resin adhesive agent layers: aglass plate 3 mm in thickness, the above-mentioned produced film 400 μmin thickness; a bi-axially drawn polyethylene terephthalate film 38 μmin thickness in which solar cell elements made of amorphous silicon werearranged in parallel; the above-mentioned produced film 400 μm inthickness; and a lamination sheet composed of a polyvinyl fluoride resinsheet (PVF) 38 μm in thickness, an aluminum foil 30 μm in thickness anda polyvinyl fluoride resin sheet (PVF) 38 μm in thickness, as a rearface protecting sheet. A vacuum laminator for solar cell moduleproduction was used to press the laminate for pre-bonding at 150° C. for15 minutes in the state that the solar cell element face thereof wasdirected upwards, and subsequently the laminate was heated at 150° C. inan oven for 15 minutes, to produce a solar cell module according to theinvention.

Even after the solar cell module was allowed to stand in a state of ahigh-temperature of 85° C. and a high-humidity of 85% for 1000 hours,the external appearance thereof did not change and the lowering of theelectromotive force was 5% or less. Even after the module was subjectedto a sunshine weatherometer test (sunshine carbon arc lamp illuminance:255 W/m², temperature: 60° C., and humidity: 60%) for 500 hours, theexternal appearance thereof did not change and the lowering of theelectromotive force was 5% or less.

Example 2

A filler sheet according to the invention and a solar cell module usedwere produced in the very same way as in Example 1 except that 0.15 partby weight of vinyltrimethoxysilane was used and the silane modificationratio was set to 0.1%.

The production state of the film, the external appearance, thetransmittance to all rays, and the peel strength after the film wasallowed to stand in a state of a high-temperature of 85° C. and ahigh-humidity of 85% for 1000 hours were the same as in Example 1.

The solar cell module produced by use of the film was allowed to standin a state of a high-temperature of 85° C. and a high-humidity of 85%for 1000 hours, and after this the external appearance and the loweringof the electromotive force were the same as in Example 1. Even after themodule was subjected to a sunshine weatherometer test (sunshine carbonarc lamp illuminance: 255 W/m², temperature: 60° C., and humidity: 60%)for 500 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less.

Example 3

Ten parts by weight of the hindered amine type light stabilizer, 10parts by weight of the benzophenone type ultraviolet absorbent and 10parts by weight of the phosphorus type thermal stabilizer were mixedwith 70 parts by weight of a silane modified linear low densitypolyethylene having a silane modification ratio of 4%, produced in thevery same way as in Example 1 except that 6 parts by weight ofvinyltrimethoxysilane was used, and then the mixture was melted andworked into a master batch.

In the same way as in Example 1 except that to 100 parts by weight ofthe silane-modified linear low density polyethylene were added 26 partsby weight of the master batch, a film 400 μm in thickness was formed.

The production state of the film, the external appearance, thetransmittance to all rays, and the peel strength after the film wasallowed to stand in a state of a high-temperature of 85° C. and ahigh-humidity of 85% for 1000 hours were the same as in Example 1.

The solar cell module produced by use of the film was allowed to standin a state of a high-temperature of 85° C. and a high-humidity of 85%for 1000 hours, and after this the external appearance and the loweringof the electromotive force were the same as in Example 1. Even after themodule was subjected to a sunshine weatherometer test (sunshine carbonarc lamp illuminance: 255 W/m², temperature: 60° C., and humidity: 60%)for 500 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less.

Example 4

Three parts by weight of the hindered amine type light stabilizer, 6parts by weight of the benzophenone type ultraviolet absorbent and 6parts by weight of the phosphorus type thermal stabilizer were mixedwith 85 parts by weight of a silane modified linear low densitypolyethylene having a silane modification ratio of 2%, produced in thesame way as in Example 1, and then the mixture was melted and workedinto a master batch.

In the same way as in Example 1 except that to 100 parts by weight ofthe silane-modified linear low density polyethylene was added 1 part byweight of the master batch, a film 400 μm in thickness was formed.

The production state of the film, the external appearance, thetransmittance to all rays, and the peel strength after the film wasallowed to stand in a state of a high-temperature of 85° C. and ahigh-humidity of 85% for 1000 hours were the same as in Example 1.

The solar cell module produced by use of the film was allowed to standin a state of a high-temperature of 85° C. and a high-humidity of 85%for 1000 hours, and after this the external appearance and the loweringof the electromotive force were the same as in Example 1. Even after themodule was subjected to a sunshine weatherometer test (sunshine carbonarc lamp illuminance: 255 W/m², temperature: 60° C., and humidity: 60%)for 500 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less.

Example 5

Three parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%.

Next, 2.5 parts by weight of the hindered amine type light stabilizer,3.5 parts by weight of the benzophenone type ultraviolet absorbent and 5parts by weight of the phosphorus type thermal stabilizer were mixedwith 89 parts by weight of linear low density polyethylene, and then themixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 5 parts by weight of the master batch, and theresultant resin was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength thereof to a frontface protecting sheet, a rear face protecting sheet and a cell, the filmwas not easily peeled and in a good state even after the module wasallowed to stand in a state of a high-temperature of 85° C. and ahigh-humidity of 85% for 1000 hours. After the module was subjected to asunshine weatherometer test (sunshine carbon arc lamp illuminance:255W/m², temperature: 60° C., and humidity: 60%) for 500 hours, the filmwas not easily peeled and was in a good state.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. Even after the solar cell module was allowed to stand in astate of a high-temperature of 85° C. and a high-humidity of 85% for1000 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less. Even after themodule was subjected to a sunshine weatherometer test (sunshine carbonarc lamp illuminance: 255 W/m², temperature: 60° C., and humidity: 60%)for 500 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less.

Example 6

To 20 parts by weight of the silane-modified linear low densitypolyethylene produced in Example 5 were added 80 parts by weight oflinear low density polyethylene and 5 parts by weight of the masterbatch produced in Example 5. The mixture of the silane-modified linearlow density polyethylene, the linear low density polyethylene and themaster batch was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the film was not easily peeled and in a good state even after the modulewas allowed to stand in a state of a high-temperature of 85° C. and ahigh-humidity of 85% for 1000 hours. After the module was subjected to asunshine weatherometer test (sunshine carbon arc lamp illuminance: 255W/m², temperature: 60° C., and humidity: 60%) for 500 hours, the filmwas not easily peeled and was in a good state.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. Even after the solar cell module was allowed to stand in astate of a high-temperature of 85° C. and a high-humidity of 85% for1000 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less. Even after themodule was subjected to a sunshine weatherometer test (sunshine carbonarc lamp illuminance: 255 W/m², temperature: 60° C., and humidity: 60%)for 500 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less.

Example 7

0.0001 part by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 0.0001%.

Next, 2.5 parts by weight of the hindered amine type light stabilizer,3.5 parts by weight of the benzophenone type ultraviolet absorbent and 5parts by weight of the phosphorus type thermal stabilizer were mixedwith 89 parts by weight of linear low density polyethylene, and then themixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 5 parts by weight of the master batch, and theresin was formed into a film 400 μm in thickness by T-die extrusion inthe same way as in Example 1.

The peel strength of the above-mentioned resultant film to a front faceprotecting sheet, a rear face protecting sheet and a cell was poorerthan those of Examples 1 to 6 but was within a practically sufficientrange.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, interlayer peeling of the film from the front face protectingsheet, the rear face protecting sheet and the cell was partiallyobserved, and the lowering of the electromotive force was over 5% butwas within a practically sufficient range.

Example 8

Forty parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 3%.

Next, 2.5 parts by weight of the hindered amine type light stabilizer,3.5 parts by weight of the benzophenone type ultraviolet absorbent and 5parts by weight of the phosphorus type thermal stabilizer were mixedwith 89 parts by weight of linear low density polyethylene, and then themixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 5 parts by weight of the master batch, and afilm400 μm in thickness was formed by T-die extrusion in the same way asin Example 1.

The peel strength of the above-mentioned resultant film to a front faceprotecting sheet, a rear face protecting sheet and a cell was poorerthan those of Examples 1 to 6 but was within a practically sufficientrange.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, interlayer peeling of the film from the front face protectingsheet, the rear face protecting sheet and the cell was partiallyobserved, and the lowering of the electromotive force was over 5% butwas within a practically sufficient range.

Example 9

Three parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%.

Next, 2.5 parts by weight of the hindered amine type light stabilizer,0.001 part by weight of the benzophenone type ultraviolet absorbent and5 parts by weight of the phosphorus type thermal stabilizer were mixedwith 92.5 parts by weight of linear low density polyethylene, and thenthe mixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 5 parts by weight of the master batch, and theresultant resin was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the stability was unable to be kept and the film was partially peeledafter the module was subjected to a sunshine weatherometer test(sunshine carbon arc lamp illuminance: 255 W/m², temperature: 60° C.,and humidity: 60%) for 500 hours. Thus, the peel strength stability waspoorer than those of Examples 1 to 6 but was within a practicallysufficient range.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was subjected to a sunshineweatherometer test (sunshine carbon arc lamp illuminance: 255 W/m²,temperature: 60° C., and humidity: 60%) for 500 hours, the lowering ofthe electromotive force was over 5% but was within a practicallysufficient range.

Example 10

Three parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%.

Next, 0.001 part by weight of the hindered amine type light stabilizer,2.5 parts by weight of the benzophenone type ultraviolet absorbent and 5parts by weight of the phosphorus type thermal stabilizer were mixedwith 91.5 parts by weight of linear low density polyethylene, and thenthe mixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 5 parts by weight of the master batch, and theresultant resin was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the stability was unable to be kept and the film was partially peeledafter the module was subjected to a sunshine weatherometer test(sunshine carbon arc lamp illuminance: 255 W/m², temperature: 60° C.,and humidity: 60%) for 500 hours. Thus, the peel strength stability waspoorer than those of Examples 1 to 6 but was within a practicallysufficient range.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was subjected to a sunshineweatherometer test (sunshine carbon arc lamp illuminance: 255 W/m²,temperature: 60° C., and humidity: 60%) for 500 hours, the lowering ofthe electromotive force was over 5% but was within a practicallysufficient range.

Example 11

Three parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%.

Next, 3.5 parts by weight of the hindered amine type light stabilizer,2.5 parts by weight of the benzophenone type ultraviolet absorbent and0.001 part by weight of the phosphorus type thermal stabilizer weremixed with 89 parts by weight of linear low density polyethylene, andthen the mixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 5 parts by weight of the master batch, and theresultant resin was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1. As a result, the resin wasoxidized, deteriorated and thermally crosslinked at the time of theextrusion, so that heterogeneous gelation was locally observed in theexternal appearance of the above-mentioned resultant film. However, thefilm was practically sufficient.

Example 12

Three parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%.

Next, 2.5 parts by weight of the hindered amine type light stabilizer,60 parts by weight of the benzophenone type ultraviolet absorbent and 5parts by weight of the phosphorus type thermal stabilizer were mixedwith 32.5 parts by weight of linear low density polyethylene, and thenthe mixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 10 parts by weight of the master batch, and theresultant resin was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the stability was unable to be kept and the film was partially peeledafter the module was allowed to stand in a state of a high-temperatureof 85° C. and a high-humidity of 85% for 1000 hours. Thus, the peelstrength stability was poorer than those of Examples 1 to 6 but waswithin a practically sufficient range.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, the lowering of the electromotive force was over 5% but waswithin a practically sufficient range.

Example 13

Three parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%.

Next, 60 parts by weight of the hindered amine type light stabilizer,2.5 parts by weight of the benzophenone type ultraviolet absorbent and 5parts by weight of the phosphorus type thermal stabilizer were mixedwith 32.5 parts by weight of linear low density polyethylene, and thenthe mixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 10 parts by weight of the master batch, and theresultant resin was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the stability was unable to be kept and the film was partially peeledafter the module was allowed to stand in a state of a high-temperatureof 85° C. and a high-humidity of 85% for 1000 hours. Thus, the peelstrength stability was poorer than those of Examples 1 to 6 but waswithin a practically sufficient range.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, the lowering of the electromotive force was over 5% but waswithin a practically sufficient range.

Example 14

Three parts by weight of vinylmethoxysilane and 0.1 part by weight of afree radical generator (t-butyl-peroxyisobutyrate) were mixed with 100parts by weight of linear low density polyethylene, and the polyethylenewas graft-polymerized at an extrusion temperature of 200° C. to preparea silane-modified linear low density polyethylene having a silanemodification ratio of 2%.

Next, 3.5 parts by weight of the hindered amine type light stabilizer,2.5 parts by weight of the benzophenone type ultraviolet absorbent and60 parts by weight of the phosphorus type thermal stabilizer were mixedwith 32.5 parts by weight of linear low density polyethylene, and thenthe mixture was melted and worked into a master batch.

To 100 parts by weight of the silane-modified linear low densitypolyethylene were added 10 parts by weight of the master batch, and theresultant resin was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the stability was unable to be kept and the film was partially peeledafter the module was allowed to stand in a state of a high-temperatureof 85° C. and a high-humidity of 85% for 1000 hours. Thus, the peelstrength stability was poorer than those of Examples 1 to 6 but waswithin a practically sufficient range.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, the lowering of the electromotive force was over 5% but waswithin a practically sufficient range.

Example 15

To 20 parts by weight of the silane-modified linear low densitypolyethylene produced in Example 5 were added 99.99 parts by weight oflinear low density polyethylene and 5 parts by weight of the masterbatch produced in Example 5. The mixture of the silane modified linearlow density polyethylene, the linear low density polyethylene and themaster batch was formed into a film 400 μm in thickness by T-dieextrusion in the same way as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. The peel strength of the above-mentionedresultant film to a front face protecting sheet, a rear face protectingsheet and a cell was low, and the film was partially peeled. The peelstrength was poorer than those of Examples 1 to 6 but was within apractically sufficient range.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, interlayer peeling of the film from the front face protectingsheet, the rear face protecting sheet and the cell was observed, and thelowering of the electromotive force was over 5% but was within apractically sufficient range.

Example 16

(1) Production of a Filler Sheet (B)

The following were mixed with each other: 100 parts by weight of alinear low density polyethylene synthesized by copolymerizing ethylenewith 1-butene at a ratio of 8% by weight; 2 parts by weight of maleicanhydride; and 3 parts by weight of a free radical generator(t-butyl-peroxybenzoate). The polyethylene was graft-polymerized at anextrusion temperature of 200° C. to prepare a maleic anhydride modifiedlinear low density polyethylene having a maleic anhydride modificationratio of 0.08%. With 85 parts by weight of the resultant polyethylenewere mixed 2.5 parts by weight of a hindered amine type lightstabilizer, 7.5 parts by weight of a benzophenone type ultravioletabsorbent and 5 parts by weight of a phosphorus type thermal stabilizer,and then the mixture was melted and worked into a master batch.

The weight-average molecular weight of the maleic anhydride modifiedlinear low density polyethylene was 33,700 as measured by a gelpermeation chromatography method (GPC method). The ratio of theweight-average molecular weight (Mw) to the number-average molecularweight (Mn), (Mw/Mn), was 1.01.

To 100 parts by weight of the maleic anhydride modified linear lowdensity polyethylene were added 5 parts by weight of the master batch,and then a film-forming machine having an extruder 25 mm in diameter anda T die 300 mm in width was used to form the resin into a film 400 μm inthickness at a resin temperature of 230° C. and a pulling-out rate of 3m/minute.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays.

About the peel strength thereof, the film was not easily peeled and wasin a good state even after the module was allowed to stand in a state ofa high-temperature of 85° C. and a high-humidity of 85% for 1000 hours.

(2) Production of a Solar Cell Module

The above-mentioned produced film was used as a filler sheet, and thefollowing were laminated: an ETFE, 50 μm in thickness, subjected toatmospheric pressure plasma treatment as a front face protecting sheet;the above-mentioned produced film 400 μm in thickness; a polyimide film,50 μm in thickness, where solar cell elements made of amorphous siliconwere arranged in parallel; the above-mentioned produced film 400 μm inthickness; and a color steel plate, 500 μm in thickness, where apolyester coating film was applied onto a galvanium steel plate obtainedby covering a steel plate with an alloy of zinc and aluminum, as a rearface protecting sheet. A laminator for solar cell module production wasused to press the laminate for pre-bonding at 150° C. for 15 minutes inthe state that the solar cell element face thereof was directed upwards,and subsequently the laminate was heated at 150° C. in an oven for 15minutes, to produce a solar cell module according to the invention.

Even after the solar cell module was allowed to stand in a state of ahigh-temperature of 85° C. and a high-humidity of 85% for 1000 hours,the external appearance thereof did not change and the lowering of theelectromotive force was 5% or less.

Example 17

The following were mixed with each other: 100 parts by weight of alinear low density polyethylene synthesized by copolymerizing ethylenewith 1-butene at a ratio of 8% by weight; 2 parts by weight of maleicanhydride; and 3 parts by weight of a free radical generator(t-butyl-peroxybenzoate). The polyethylene was graft-polymerized at anextrusion temperature of 200° C. to prepare a maleic anhydride modifiedlinear low density polyethylene having a maleic anhydride modificationratio of 0.08%.

Next, 5 parts by weight of the phosphorus type thermal stabilizer weremixed with 95 parts by weight of linear low density polyethylene, andthen the mixture was melted and worked into a master batch.

To 100 parts by weight of the maleic anhydride modified linear lowdensity polyethylene were added 5 parts by weight of the master batch,and the resultant resin was formed into a film 400 μm in thickness byT-die extrusion in the same manner as in Example 1,

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the film was not easily peeled and was in a good state even after themodule was allowed to stand in a state of a high-temperature of 85° C.and a high-humidity of 85% for 1000 hours.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. Even after the solar cell module was allowed to stand in astate of a high-temperature of 85° C. and a high-humidity of 85% for1000 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less.

Example 18

To 20 parts by weight of the maleic anhydride modified linear lowdensity polyethylene produced in Example 17 were added 80 parts byweight of linear low density polyethylene and 5 parts by weight of themaster batch produced in Example 17. The mixture of the maleic anhydridemodified linear low density polyethylene, the linear low densitypolyethylene and the master batch was formed into a film 400 μm inthickness by T-die extrusion in the same manner as in Example 1.

The film-formation was carried out without any difficulty. Theabove-mentioned resultant film was good in external appearance andtransmittance to all rays. About the peel strength stability thereof toa front face protecting sheet, a rear face protecting sheet and a cell,the film was not easily peeled and was in a good state even after themodule was allowed to stand in a state of a high-temperature of 85° C.and a high-humidity of 85% for 1000 hours.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. Even after the solar cell module was allowed to stand in astate of a high-temperature of 85° C. and a high-humidity of 85% for1000 hours, the external appearance thereof did not change and thelowering of the electromotive force was 5% or less.

Example 19

The following were mixed with each other: 100 parts by weight of alinear low density polyethylene synthesized by copolymerizing ethylenewith 1-butene at a ratio of 8% by weight; 0.001 part by weight of maleicanhydride; and 3 parts by weight of a free radical generator(t-butyl-peroxybenzoate). The polyethylene was graft-polymerized at anextrusion temperature of 200° C. to prepare a maleic anhydride modifiedlinear low density polyethylene having a maleic anhydride modificationratio of 0.0001%.

Next, 5 parts by weight of the phosphorus type thermal stabilizer weremixed with 95 parts by weight of linear low density polyethylene, andthen the mixture was melted and worked into a master batch.

To 100 parts by weight of the maleic anhydride modified linear lowdensity polyethylene were added 5 parts by weight of the master batch,and then the resultant resin was formed into a film 400 μm in thicknessby T-die extrusion in the same manner as in Example 1. Thefilm-formation was carried out without any difficulty.

The peel strength of the above-mentioned resultant film to a front faceprotecting sheet, a rear face protecting sheet and a cell was low andthe film was partially peeled. Thus, the peel strength was poorer thanthose of Examples 16 to 18 but was within a practically sufficientrange.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, interlayer peeling of the film from the front face protectingsheet, the rear face protecting sheet and the cell was partiallyobserved, and the lowering of the electromotive force was over 5% butwas within a practically sufficient range.

Example 20

The following were mixed with each other: 100 parts by weight of alinear low density polyethylene synthesized by copolymerizing ethylenewith 1-butene at a ratio of 8% by weight; 40 parts by weight of maleicanhydride; and 3 parts by weight of a free radical generator(t-butyl-peroxybenzoate). The polyethylene was graft-polymerized at anextrusion temperature of 200° C. to prepare a maleic anhydride modifiedlinear low density polyethylene having a maleic anhydride modificationratio of 0.1%.

Next, 5 parts by weight of the phosphorus type thermal stabilizer weremixed with 95 parts by weight of linear low density polyethylene, andthen the mixture was melted and worked into a master batch.

To 100 parts by weight of the maleic anhydride modified linear lowdensity polyethylene were added 5 parts by weight of the master batch,and then the resultant resin was formed into a film 400 μm in thicknessby T-die extrusion in the same manner as in Example 1.

The peel strength of the above-mentioned resultant film to a front faceprotecting sheet, a rear face protecting sheet and a cell was low andthe film was partially peeled. Thus, the peel strength was poorer thanthose of Examples 16 to 18 but was within a practically sufficientrange.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, interlayer peeling of the film from the front face protectingsheet, the rear face protecting sheet and the cell was observed, and thelowering of the electromotive force was over 5% but was within apractically sufficient range.

Example 21

To 20 parts by weight of the maleic anhydride modified linear lowdensity polyethylene produced in Example 17 were added 99.99 parts byweight of linear low density polyethylene and 5 parts by weight of themaster batch produced in Example 17. The mixture of the maleic anhydridemodified linear low density polyethylene, the linear low densitypolyethylene and the master batch was formed into a film 400 μm inthickness by T-die extrusion in the same manner as in Example 1. Thefilm-formation was carried out without any difficulty.

The peel strength of the above-mentioned resultant film to a front faceprotecting sheet, a rear face protecting sheet and a cell was low andthe film was partially peeled. Thus, the peel strength was poorer thanthose of Examples 16 to 18 but was within a practically sufficientrange.

The above-mentioned produced film was used as a filler sheet to producea solar cell module according to the invention in the same way as inExample 1. After the solar cell module was allowed to stand in a stateof a high-temperature of 85° C. and a high-humidity of 85% for 1000hours, interlayer peeling of the film from the front face protectingsheet, the rear face protecting sheet and the cell was observed, and thelowering of the electromotive force was over 5% but was within apractically sufficient range.

Comparative Example 1

A glass plate 3 mm in thickness as a substrate was used as a front faceprotecting sheet for a solar cell module. Onto one face thereof werethen laminated an ethylene-vinyl acetate copolymer sheet 400 μm inthickness, a bi-axially drawn polyethylene terephthalate film 38 μm inthickness in which solar cell elements made of amorphous silicon werearranged in parallel, an ethylene-vinyl acetate copolymer sheet 400 μmin thickness, and a bi-axially drawn polyethylene terephthalate film 50μm in thickness as a rear face protecting sheet through acrylic resinadhesive agent layers in such a manner that the solar cell element facethereof was directed upwards. The same way as in Example 1 was carriedout to produce a solar cell module.

Comparative Example 2

A glass plate 3 mm in thickness as a substrate was used as a front faceprotecting sheet for a solar cell module. Onto one face thereof werethen laminated a low density polyethylene sheet 400 μm in thickness, abi-axially drawn polyethylene terephthalate film 38 μm in thickness inwhich solar cell elements made of amorphous silicon were arranged inparallel, a low density polyethylene sheet 400 μm in thickness, and alamination sheet composed of a polyvinyl fluoride resin sheet (PVF) 38μm in thickness, an aluminum foil 30 μm in thickness, and a polyvinylfluoride resin sheet (PVF) 38 μm in thickness as a rear face protectingsheet through acrylic resin adhesive agent layers. In the state that thesolar cell element face thereof was directed upwards, the same way as inExample 1 was carried out to produce a solar cell module.

Experiment Example

The solar cell modules produced by use of the filler sheets according tothe invention produced in Examples 1 to 21 and the solar cell modulesproduced by use of the filler layers according to Comparative Examples 1and 2 were allowed to stand in a state of a high-temperature of 85° C.and a high-humidity of 90% for 1000 hours. Thereafter, thetransmittances thereof to all rays were measured, and further a solarcell module evaluating test was made.

(1) Measurement of Transmittance to All Rays

About the filler sheets used to produce the solar cell modules of theinvention in Examples 1 to 21 and the filler layers used to produce thesolar cell modules in Comparative Examples 1 and 2, the transmittances(%) thereof to all rays were measured with a color computer.

(2) Solar Cell Module Evaluating Test

About the solar cell modules produced by use of the filler sheetsaccording to Examples 1 to 21 and the solar cell modules produced by useof the filler layers according to Comparative Examples 1 and 2, a solarcell module environmental test was made based on JIS standardC8917-1989. The photoelectromotive force outputs therefrom before andafter the test were measured, and then the results were compared andevaluated.

(3) Measurement of Peel Strength of Filler Layer

A cut of 15 mm width was made in the rear face protecting sheet of therear outermost face and the filler sheet (filler layer) positionedinside it (of each of the modules).

Next, 90-degree peeling was performed at a peel rate of 50 mm/minute atthe interface between the polyimide film 38 μm in thickness, where thesolar cell elements with the cut of 15 mm width were arranged inparallel, and the filler sheet (filler layer), so as to measure the peelstrength.

(4) Measurement of Peel Strength Stability of Filler Layer to Rear FaceProtecting Sheet

The solar cell modules produced by use of the filler sheets (fillerlayers) according to Examples 1 to 21 and the solar cell modulesproduced by use of the filler layers according to Comparative Examples 1and 2 were allowed to stand in a state of a high-temperature of 85° C.and a high-humidity of 90% for 1000 hours, and subsequently a cut of 15mm width was made in the rear face protecting sheet of the rearoutermost face (of each of the modules). At the interface between therear face protecting sheet and the filler sheet (filler layer), in whichthe cut of 15 mm width was made, the peel strengths before and after thehigh-temperature and high-humidity test were measured and compared forevaluation.

(5) Measurement of Peel Strength Stability of Filler Layer to Front FaceProtecting Sheet

The solar cell modules produced by use of the filler sheets (fillerlayers) according to Examples 1 to 21 and the solar cell modulesproduced by use of the filler layers according to Comparative Examples 1and 2 were allowed to stand in a state of a high-temperature of 85° C.and a high-humidity of 90% for 1000 hours. Thereafter, a cut of 15 mmwidth was made in the front face protecting sheet of the front outermostface (of each of the modules), or the rear face protecting sheet of therear outermost face, the filler sheet (filler layer) and the film inwhich the solar cell elements were arranged in parallel, which werepositioned inside the rear face protecting sheet, and the filler sheet(filler layer) positioned at the inner side thereof. At the interfacebetween the front face protecting sheet and the filler sheet (fillerlayer), in which the cut of 15 mm width was made, the peel strengthsbefore and after the high-temperature and high-humidity test weremeasured and compared for evaluation.

(6) Measurement of Peel Strength Stability of Filler Layer to Solar CellElement (Cell)

The solar cell modules produced by use of the filler sheets (fillerlayers) according to Examples 1 to 21 and the solar cell modulesproduced by use of the filler layers according to Comparative Examples 1and 2 were allowed to stand in a state of a high-temperature of 85° C.and a high-humidity of 90% for 1000 hours. Thereafter, a cut of 15 mmwidth was made in the front face protecting sheet of the front outermostface (of each of the modules), or the rear face protecting sheet of therear outermost face, the filler sheet (filler layer) and the film inwhich the solar cell elements were arranged in parallel, which werepositioned inside the rear face protecting sheet, and the filler sheet(filler layer) positioned at the inner side thereof. At the interfacebetween the solar cell element and the filler sheet (filler layer), inwhich the cut of 15 mm width was made, the peel strengths before andafter the high-temperature and high-humidity test were measured andcompared for evaluation.

Results of the above-mentioned measurement are shown in Table 1. TABLE 1High temperature and Sunshine weatherometer high humidity for 1000 hourstest for 500 hours Adhesive Adhesive Peel strength stability to AdhesiveAdhesive stability to Lowering of filler sheet rear face stability tofront Adhesive stability to rear front face Adhesive Transmittance ratioof (N/15 mm protecting face protecting stability to cell face protectingprotecting stability to cell to all rays (%) output (%) width) sheet (%)sheet (%) (%) sheet (%) sheet (%) (%) Example 1 91 −3 23 96 96 96 96 9696 Example 2 92 −2 24 92 94 — — — — Example 3 91 −3 24 98 97 — — — —Example 4 91 −2 22 96 97 — — — — Example 5 92 −2 25 95 95 95 95 95 95Example 6 94 −1 27 94 94 94 94 94 94 Example 7 93 −15 1 — — — — — —Example 8 91 −16 5 — — — — — — Example 9 92 −20 26 96 96 96 30 30 30Example 10 93 −23 23 95 95 95 38 38 38 Example 11 82 −12 20 90 90 90 9090 90 Example 12 92 −25 21 30 30 30 30 30 30 Example 13 91 −26 22 38 3838 38 38 38 Example 14 93 −28 20 38 38 38 38 38 38 Example 15 94 −18 0.5— — — — — — Example 16 92 −3 23 85 92 96 85 92 96 Example 17 93 −2 26 8592 96 85 92 96 Example 18 91 −4 23 85 92 96 85 92 96 Example 19 94 −13 1— — — — — — Example 20 93 −15 2 — — — — — — Example 21 92 −14 1 — — — —— — Comparative 89 −50 16 30 86 85 — — — Example 1 Comparative 92 −430.2   0.2   0.1   0.1 — — — Example 2

As is evident from the measurement results shown in Table 1, the fillersheets according to Examples 1 to 21 had a high transmittance to allrays and a low output lowering ratio, and were practically sufficient.Furthermore, the filler sheet according to Examples 1 to 21 wereexcellent in peel strength and were also excellent in peel strengthstability to the front face protecting sheet and the rear faceprotecting sheet.

On the other hand, filler layers according to Comparative Examples 1 and2 had a high transmittance to all rays but the solar cell modules usingthe layers had problems such as that the output lowering ratio was high.Furthermore, the filler layers according to Comparative Examples 1 and 2were poor in peel strength and also low in adhesive stability to therespective protecting sheets.

1. A filler sheet for a solar cell module, which is formed as a fillersheet laminated on front face and rear face sides of a solar cellelement, and is made of a resin film produced by a resin compositioncomprising a copolymer of an α-olefin and an ethylenic unsaturatedsilane compound, or a modified or condensed body thereof, and one ormore selected from a group consisting of a light resisting agent, anultraviolet absorbent and a thermal stabilizer.
 2. The filler sheet fora solar cell module according to claim 1, wherein the α-olefin is one ormore selected from a group consisting of ethylene, propylene, 1-butene,isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene,1-heptene, 1-octene, 1-nonene, and 1-decene.
 3. The filler sheet for asolar cell module according to claim 1 or 2, wherein the ethylenicunsaturated silane compound is one or more selected from a groupconsisting of vinyltrimethoxysilane, vinyltriethoxysilane,vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane,vinyltripentyloxysilane, vinyltriphenoxysilane, vinyltribenzyloxysilane,vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane,vinylpropionyloxysilane, vinyltriacetoxysilane, andvinyltricarboxysilane.
 4. The filler sheet for a solar cell moduleaccording to any one of claims 1 to 3, wherein the copolymer of theα-olefin and the ethylenic unsaturated silane compound is a copolymerwhich further comprises one or more selected from a group consisting ofvinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, methylmethacrylate, ethyl acrylate, and vinyl alcohol.
 5. A filler sheet forsolar cell, which is formed as a filler sheet laminated on front faceand rear face sides of a solar cell element, and is made of a resin filmproduced by a resin composition comprising a maleic anhydride modifiedpolyolefin.
 6. The filler sheet for solar cell according to claim 5,wherein the resin composition further comprises one or more selectedfrom a group consisting of a light resisting agent, an ultravioletabsorbent and a thermal stabilizer.
 7. The filler sheet for solar cellaccording to claim 5 or 6, wherein the maleic anhydride modifiedpolyolefin is a substance modified by graft-copolymerizing a polyolefinwith maleic anhydride, and a content ratio of maleic anhydride in themaleic anhydride modified polyolefin ranges from 0.001 to 30% by weight.8. The filler sheet for solar cell according to any one of claims 5 to7, wherein the maleic anhydride modified polyolefin has a weight-averagemolecular weight of 1,000 to 1300,000, the molecular weight beingobtained by a gel permeation chromatography, and a ratio of theweight-average molecular weight (Mw) to a number-average molecularweight (Mn), (Mw/Mn), is 6 or less.
 9. The filler sheet for a solar cellmodule according to any one of claims 1 to 8, wherein the lightresisting agent is made of a hindered amine type light stabilizer. 10.The filler sheet for a solar cell module according to any one of claims1 to 9, wherein the ultraviolet absorber is made of a benzophenone type,triazole type, salicylic acid derivative type, or acrylonitrilederivative type ultraviolet absorbent.
 11. The filler sheet for a solarcell module according to any one of claims 1 to 10, wherein the thermalstabilizer is made of a phosphorus type thermal stabilizer, a phenoltype thermal stabilizer, or a lactone type thermal stabilizer.
 12. Thefiller sheet for a solar cell module according to any one of claims 1 to11, wherein the light resisting agent is contained at a content ratio of0.01 to 5% by weight of the copolymer of the α-olefin and the ethylenicunsaturated silane compound, or the modified or condensed body thereof,or the maleic anhydride modified polyolefin.
 13. The filler sheet for asolar cell module according to any one of claims 1 to 12, wherein theultraviolet absorbent is contained at the content ratio of 0.05 to 5% byweight of the copolymer of the α-olefin and the ethylenic unsaturatedsilane compound, or the modified or condensed body thereof, or themaleic anhydride modified polyolefin.
 14. The filler sheet for a solarcell module according to any one of claims 1 to 13, wherein the thermalstabilizer is contained at the content ratio of 0.05 to 5% by weight ofthe copolymer of the α-olefin and the ethylenic unsaturated silanecompound, or the modified or condensed body thereof, or the maleicanhydride modified polyolefin.
 15. A solar cell module made bylaminating a front face protecting sheet, a filler sheet, a solar cellelement, a filler sheet and a rear face protecting sheet in sequence soas to be integrated, wherein the filler sheets are each the filler sheetfor a solar cell module according to any one of claims 1 to
 14. 16. Thesolar cell module according to claim 15, wherein the front faceprotecting sheet is made of a glass plate, a fluorine-contained resinsheet, a cyclic polyolefine resin sheet, a polycarbonate resin sheet, apoly(meth)acrylic resin sheet, a polyamide resin sheet, or a polyesterresin sheet.
 17. The solar cell module according to claim 15 or 16,wherein the solar cell element is made of a crystal silicon solar cellelement or an amorphous silicon solar cell element.
 18. The solar cellmodule according to any one of claims 15 to 17, wherein the rear faceprotecting sheet is made of a metal plate or metal foil, thefluorine-contained resin sheet, the cyclic polyolefine resin sheet, thepolycarbonate resin sheet, the poly(meth)acrylic resin sheet, thepolyamide resin sheet, or the polyester resin sheet.
 19. The solar cellmodule according to any one of claims 15 to 18, wherein the front faceprotecting sheet and the filler sheet are beforehand laminated andintegrated with each other.
 20. The solar cell module according to anyone of claims 15 to 19, wherein the rear face protecting sheet and thefiller sheet are beforehand laminated and integrated with each other.21. The solar cell module according to any one of claims 15 to 20,wherein a gel fraction in each of the filler sheets is 10% or less.